Axial pressure balancing means for a hydraulic device

ABSTRACT

An axial, pressure-balancing arrangement for a hydraulic device of the gerotor type wherein an externally-toothed member is eccentrically received within an internally-toothed member to form a plurality of expanding and contracting volume chambers by teeth interaction. The arrangement includes a sealing plate juxtaposed an axial end face of the toothed members and a plurality of especially configured sealed pockets disposed on the opposite side of the sealing plate. The sealed pockets are orientated so that each pocket is axially aligned with a particular volume chamber. The sealing plate has a plurality of radially-spaced ports orientated so that each port is in constant communication with a particular volume chamber and a sealed pocket associated with that particular volume chamber. Each sealed pocket defines a predetermined pressurizable area on the sealing plate which is a function of the cross-sectional area of the associated volume chamber at maximum displacement. Pressure in each volume chamber is thus communicated through the ports into the sealed pockets to produce a series of balancing forces behind the plate which are always proportional to the pressures in the respective pockets. This force is sufficient to bias the sealing plate into sealing engagement with the toothed members even though the pressure in the associated volume chambers ranges from high to low during each operational cycle of the device.

United States Patent [1 1 Swedberg [451 Mar. 4, 1975 AXIAL PRESSURE BALANCING MEANS FOR A HYDRAULIC DEVICE [75] lnventor: Nils Einar Swedberg, Chanhassen,

Minn.

[73] Assignee: Eaton Corporation, Cleveland, Ohio [22] Filed: May 21, 1973 [21] Appl. No.: 362,588

Primary I5.\'amiMerC. J. Husar Assistant Eraminer-Leonard Smith Attorney, Agent, or Ft'rntTeagn0 & Toddy {57] ABSTRACT An axial. pressure-balancing arrangement for a hy draulic device of the gerotor type wherein an externally-toothed member is eccentrically received within an internally-toothed member to form a plurality of expanding and contracting volume chambers by teeth interaction. The arrangement includes a sealing plate juxtaposed an axial end face of the toothed members and a plurality of especially configured sealed pockets disposed on the opposite side of the sealing plate. The sealed pockets are orientated so that each pocket is axially aligned with a particular volume chamber. The sealing plate has a plurality of radially-spaced ports orientated so that each port is in constant communication with a particular volume chamber and a sealed pocket associated with that particular volume chamber. Each sealed pocket defines a predetermined pressurizable area on the sealing plate which is a function of the cross-sectional area of the associated volume chamber at maximum displacement.

Pressure in each volume chamber is thus communicated through the ports into the sealed pockets to produce a series of balancing forces behind the plate which are always proportional to the pressures in the respective pockets. This force is sufficient to bias the sealing plate into sealing engagement with the toothed members even though the pressure in the associated volume chambers ranges from high to low during each operational cycle of the device.

4 Claims, 4 Drawing Figures AXIAL PRESSURE BALANCING MEANS FOR A HYDRAULIC DEVICE This invention relates generally to hydraulic devices of the gerotor type and more particularly, to an axial, end face sealing arrangement therein.

Heretofore a number of known axial sealing arrangements have been employed in hydraulic devices to improve volumetric efficiency. Most such arrangements bias a sealing plate positioned at an axial end face of the chamber-forming elements into sealing engagement therewith by porting either low or high pressure into areas behind the plate which are aligned with volume chambers at low and high pressure respectively. Such arrangements are suitable for many types of hydraulic devices having certain types of valving arrangements in that the geometry of such devices permit the pressure biasing areas to remain constantly at high or low pressure and be designed accordingly. In devices of the gerotor type having commutator-type valving, however, each volume chamber sequentially shifts between high and low pressures as the chamberforming elements interact during each operational cycle. Thus prior art devices utilizing pressurizable areas which remain at relatively constant pressure are ineffective to seal end face leakage in hydraulic devices of this type.

It is thus a principal object of the subject invention to provide in hydraulic devices of the gerotor type having commutator-type valving, an axial sealing arrangement which utilizes the pressure in each volume chamber to seal each volume chamber independently of the pressures in the other chambers and thereby effectively seal an entire end face of the gerotor arrangement without excessive over or underbalancing in the low and high pressure chamber areas respectively.

In accordance with the invention, this object is achieved by providing a known gerotor arrangement having commutator-type valving comprising an internally-toothed ring member eccentrically receiving an externally-toothed star member to define a number of expanding and contracting volume chambers. An arrangement similar to this is shown in U.S. Pat. No. 25,291 and assigned to the Assignee of the present invention. Adjacent one axial end face of the toothed members is a sealing plate having a plurality of ports extending therethrough with each port in constant communication with a particular volume chamber. A like number of sealed pockets, each pocket having a surface area greater than the cross-sectional area of the associated volume chamber at maximum displacement, are disposed on the opposite side of the sealing plate. The sealed pockets may be formed in either a spider plate abutting the sealing plate or in the gerotor housing. These pockets are orientated with respect to the volume chambers and the ports so that each sealed chamber is in constant communication with a particular port and a volume chamber. Pressure in any given volume chamber, which ranges from low to high as the device completes one operational cycle, is thus communicated to its respective sealed pocket. The design and configuration of each sealed pocket is such to establish a balancing force which biases the sealing plate into sealing engagement with each volume chamber.

In accordance with another aspect of the invention, use of a sealing plate to prevent end face leakage will permit the gerotor housing adjacent the sealing plate to slightly deflect under axial load without detrimental results. Thus, current housing designs can be modified to provide increased output shaft bearing capacity for a given housing size, or alternatively, a shorter-length housing than heretofore required for a given motor capacity.

It is thus a secondary object of the invention to provide an axial, pressure-balancing arrangement in a hydraulic device of the gerotor type which permits modifications to the housing construction to provide for a more efficient and economical device.

It is yet another object of the invention to provide an axial pressure-balancing arrangement for one object in a device of the gerotor type which enables the device tohave high starting and running torque characteristics at high volumetric efficiency.

The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail herein and illustrated in the accompanying drawings which form a part hereof and wherein:

FIG. 1 is a longitudinal sectional view of the fluidoperated motor of the subject invention;

FIG. 2 is a sectional view taken along line 22 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. I; and

FIG. 4 is an elevation view of the sealing plate.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIG. 1 shows a fluid-operated motor 10, it being understood that the term motor when applied to such fluid-operated devices also encompasses the use of such devices as pumps". Motor 10 is generally cylindrical in shape and comprises several portions secured together, including an end cap 12, a gerotor arrangement or set 14 and a port plate 16 intermediate the end cap and gerotor set. Adjacent the opposite end of gerotor set 14, the motor portions to which this invention particularly relates include in their respective positions, a sealing plate 18, a spider plate 20 and a shaft housing 22 comprising a rear retainer casting 23 and a front retainer casting 24. The basic construction and operation of such a motor 10 is known to those skilled in the art and will be better understood than will be explained herein by reference to U.S. Pat. No. 3,572,982 to H. McDermott and assigned to the Assignee of the present invention.

Briefly, end cap portion 12 includes an inlet and an outlet port 25,26 and a valving member 27-rotatably disposed therein. Valving member 27 has a plurality of N-l (6) passages 28 adapted to be in communication with inlet port 25 at high pressure: and a plurality of N-l (6) passages 29 adapted to be in communication with outlet port 26 at low pressure.

Port plate 16 has a plurality of N (7) radially-spaced port passages 30 extending therethrough. Each port plate passage 30, at one end face thereof is adapted to be in communication with one of the valving member passages 28,29 at any given instant during an operational cycle. Similarly, each port passage 30 at the op posite end face of port plate 16 is adapted to be in communication with a certain volurne chamber 32 formed by the gerotor set 14.

Gerotor set 14 includes an annular splined, externally-toothed star member 33 eccentrically disposed within an internally-toothed ring member 34; the eccentricity e of the gerotor set being shown as the distance between star members axis 35 and ring members axis 36. Connected to the central opening of star member 33 by a spherical spline is a valve drive member 37 which extends through port plate 16 and terminates in a spherical splined engagement within an opening in valving member 27. Also splined to the opening of star member 33 is a main drive member 38 which extends from the opposite side of the star into shaft housing 22 where it terminates in spherical splined engagement with an output shaft 39.

Output shaft 39 is shown journalled in a tapered bearing arrangement 31, the size of which determines the rated axial and radial load capacities of the shaft. Size of the bearing arrangement 31 in turn is determined by an opening 21 formed by front and rear retainer castings 24,23 which receive the bearing arrangement 31. Front retainer casting 24 provides appropriate seals 46,47 for shaft 39 and rear retainer casting 23 provides lubricating fiow means 52 for the bearing arrangement 31.

Referring now to FIG. 2, ring member 34 is shown as having a plurality of N (7) rollers defining roller teeth 40 which interact with a plurality of N-l (6) star teeth 41 to form a plurality of N (7) volume chambers 32. In the embodiment illustrated, reference to the letter N is equivalent to the number 7 which equals the number of volume chambers 32 and ring roller teeth 40 shown and the expression N-l refers to the number 6 which equals the number of star teeth 41 shown.

As thus described, the ring and star members 34,33 will interact with each other in the usual manner. More particularly with ring member 34 fixed against rotation, the center of the star member 33 will orbit hypocycloidally about the center of the ring member 34 whereby the center of the star axis 35 will define a circle about the ring axis 36 of radius equal to the eccentricity e This movement of the star member 33 will expand and contract each one of the seven volume chambers 32 while the star member 33 rotates a peripheral distance equal to one tooth space or l/6th of a revolution. Rotation of the star member 33 thus drives the first drive member 37 which in turn rotates the valving member 27 to port high and low pressure into proper volume chambers 32 to achieve a commutator-type valving action. More particularly, with star member 33 orbiting in the direction of arrow 42, a moving line of eccentricity 43 defined as extending between ring and star axes 36,35 divides expanding volume chambers designated AB, and C at high pressure from contracting volume chambers designated DE, and F at low pressure. Volume chamber designated G is defined as a switch chamber and may momentarily be between any pressure ranging from high to low as a particular high pressure valve member passage 28 moves out of communication with its respective port passage 30 while a low pressure valve member passage 29 moves into communication therewith. Further, as star member 33 orbits about ring member 34, the line of eccentricity 43 will rotate at the star members orbital speed. Thus, when the star member 33 has completed one orbital or operation cycle, each volume chamber will have been or be at high pressure, low pressure and some differential pressure there between.

Referring now to FIGS. 1 and 4, an annular sealing plate 18 is shown abutting end face 51 of rear retainer casting 23 at one side and adjacent star and ring members axial end faces 44,45 at the other end where seal 53 is provided to prevent leakage. Sealing plate 18, approximately 1/16 inch to /5 inch thick, is constructed of a good, wear-resistant material such as high-carbon steel or alternatively could be a'bimetal plate as is known to those skilled in the art. The sealing plate 18 itself, is defined as a normally straight, flat plate which has a plurality of N ports 48 extending therethrough in spaced equal increments from one another at a fixed radial distance from the center of the sealing plate 18. More particularly as shown in FIG. 2, wherein the ports 48 are superimposed as dotted lines on gerotor set 14 for ease of explanation, each port is positioned adjacent an inner diameter 49 of the ring member 34 which defines an outer fixed wall surface for volume chambers 32. Also, each port 48 is located midway between the centers of adjacent ring rollers 40. Thus, the positioning of the ports is such that no portion of the axial end face 44 of star teeth 41 can completely cover or block the ports 48 during orbital movement of star teeth 41.

Adjacent the opposite side of sealing plate 18 is an annular spider plate 20, approximately [/16 inch thick, 7

which fits into a centrally depressed recess 50 of approximately the same size as the sealing plate which is formed in end face 51 of rear retainer casting 23. (See FIGS. 1 and 3.) The spider plate 20 may be aligned in predetermined relation within recess 50 by means of dowel pins or the like extending from housing to engage holes in spider plate 20 (not shown). An O-ring 54 extending about the periphery of spider plate 20 seals the spider plate and sealing plate 18 to insure against any leakage at the outside of the housing.

The spider plate 20 is defined as having a plurality of N generally trapezoidal-shaped, pressure biasing areas 56 extending therethrough and spaced in equal increments radially thereabout. More particularly, each trapezoidal area 56 in the embodiment illustrated, is defined by an outer curvilinear edge surface 58, an inner curvilinear edge surface 59 and radiallyextending side edge surfaces 60 which intersect inner and outer edge surfaces 59,58. Each curvilinear edge surface 58,59 is defined by an arc struck from the center of spider plate 20 and each side edge surface 60 may be defined as a radial line which, if extended, would intersect the spider plates center. Each trapezoidal area 56 is bounded by an elastic seal 61 which is molded to fit the inner, outer and side edge surfaces 59,58,60 and the intersection of these edge surfaces are rounded to prevent elastic seal 61 from being displaced therefrom. Each trapezoidal area 56 is spaced from an adjacent trapezoidal area by a land 62 which provides backing or support for the seal 61 which prevents differential pressures in adjacent pressure biasing areas 56 from adversely deforming seals 61. Each land 62 has a width of approximately /a to 3/16 of an inch in the embodiment shown. While other basically-trapezoidal area configurations may be employed for pressure biasing areas 56, test results have indicated that the surface areas of such configurations should be sized to be 10 percent greater than the maximum end face area of the volume chamber to obtain good sealing characteristics.

With respect to the geometrical relationship between pressure biasing areas 56, sealing plate 18 and gerotor set 14, it should be observed that the ports 48 of sealing plate 18 communicate with the pressure biasing areas 56 at a point midway between the outer and inner edge surfaces 58,59. (See FIG. 3 wherein ports 48 are superimposed as dotted lines on trapezoidal areas 56 for ease in explanation.) Thus, each pressure biasing area extends radially-outwardly of the ports communication point to cover or be aligned with a portion of the axial end face of each roller 40. Likewise, each trapezoidal area extends radially-inwardly to cover at least the base of each star tooth even though same be eccentrically displaced away from inner edge surface 59. Also it should be noted that the central axis 64 of each roller 40 which would intersect the center of ring member 34 if extended, also bisects each land 62 in spider plate 20.

Motor is assembled by bolts 63 which are inserted from the outside of end cap 12 and extend through end cap 12, port plate 16, ring member 34, sealing plate 18, rear retainer casting 23 and are threadably received within blind holes (not shown) formed in front retainer casting 24. To provide proper operating clearances within the motor, the axial length of each ring roller 40 is approximately 0.001 inch less than the axial length of ring member 34. Likewise, the axial length of the star member 33 is also approximately 0.001 inch less than the axial length of ring member 34. Thus, the sealing plate, when assembled in the motor 10, abuts against the axial end face 45 of ring member 34 while maintaining a 0.001 inch clearance between sealing plate 18 and the star member 33 and between sealing plate 18 and the ring rollers 40. Spider plate 20 on the opposite side of sealing plate 18 is sealed to the sealing plate and also to the front retainer casting recess 50 in the sense that the peripheral O-ring 54 and the elastic seals 61 in the pressure biasing areas 56 are compressed during assembly. More particularly, formed seals 61 and O-ring 54 are sufficiently compressed to retain their sealing characteristics under high pressure although such compressive force is not sufficient to deflect the sealing plate 18 towards the star member 33 as it is preferred that the sealing plate 18 remain flat when motor 10 is assembled.

During operation, each volume chamber 32 will supply various pressures to its respective pressure biasing area 56 and the lower portions of the sealing plate adjacent such pressure areas will deflect into sealing contact with the star member 33. Also, the upper portions of the sealing plate adjacent pressure biasing areas 56 will be biased into sealing contact with the ring member 34 to prevent leakage of fluid from volume chambers 32 into the ring rollers 40. Further, the balancing force developed as a result of the differential area of pressure biasing areas 56 is such to cause the sealing plate portions adjacent the lands 62 of the spider plate to be similarly deflected into sealing engagement with star member 33 and similarly biased into sealing engagement with ring member 34. Thus leakage at the critical point of the arrangement which occurs between adjacent volume chambers at high and low pressures, such as chambers C and D in FIG. 2, is prevented.

The sealing plate is thus deflected into sealing engagement with the star member to give high volumetric efficiency even at slow speeds and high pressures. At higher output speeds, a hydrodynamic film is developed between the star member 33 and sealing plate 18 to prevent excessive wear of the sealing plate.

Furthermore, because the spider plate 20 remains in sealing contact with the front retainer casting 24, the front retainer casting can sustain minute deflections which heretofore would result in leakage. To prevent such deflections, prior art casting designs were made rigid by integrating the front and rear castings 24,23 into a unitary casting which would be sealed at its opening by a shaft cover plate. The shaft cover plate would be bolted to the unitary casting and in accordance with casting design a thick casting wall would be required to receive the blindly threaded holes for such fasteners. This, in turn, would reduce the area of the bearing arrangement 31 which could be applied to a given motor having fixed external dimensions. Thus, the subject invention provides a larger bearing arrangement 31 for a motor of a given dimensional size than heretofore possible. Alternatively, if the bearing capacity need not be increased, the sealing plate arrangement of the subject invention will enable a shorter length motor than heretofore required.

While the invention has been explained with reference to a single sealing plate 18 employed at one axial end face of the gerotor set 14, it should be clear, as is customary in such balancing arrangements, that the invention will likewise function if a second sealing plate were employed on the opposite side of the gerotor set 14. Furthermore, while the invention has been described with reference to a spider plate 20 disposed within a recess 50 of the front retainer casting 24, the recessed pressure areas 56 could be formed in the front retainer casting 24 itself. Thus, grooves formed in trapezoidal recessed areas which could be easily cast in a powdered metal front retainer casting 24, would receive the formed seal 61 (which could comprise known O-ring and the like seals) to define the pressure biasing areas 56 and would appear identical to the view of the spider plate 20 shown in FIG. 3. The advantage of employing pressure biasing areas 56 in the casting itself as opposed to the use of a spider plate, would be that the front retainer casting could be cast as a flat surface with only the grooves to receive the formed seals 61 which would define the pressure biasing areas 56.

It is apparent that many other modifications may be incorporated into the pressure biasing arrangement of the subject invention without departing from the spirit or the essence of my invention. It is my intention to include all such modifications and alterations insofar as they come within the scope of the present invention.

It is thus the essence of the invention to provide an axial, pressure-balancing arrangement for use in hydraulic devices of the gerotor type wherein the pressure in each volume chamber is ported into an associated pressure biasing area which is so sized and orientated that the sum total of all such areas will deflect and bias the plate into sealing engagement with the chamber forming elements of the device.

Having thus defined my invention, I claim:

1. An axial pressure-balancing system for use in a rotary hydraulic device of the type including an internally-toothed member and an externally-toothed member eccentrically disposed within said internally-toothed member for relative orbital and rotational movement therebetween, said members defining a plurality of volume chambers by tooth interaction therebetween, each of said volume chambers sequentially expanding and contracting during each relative orbit between said members, each of said volume chambers having a maximum cross-sectional area on a plane generally parallel to the plane of said rotational movement, the device further including commutator-type valve means for sequentially communicating high pressure fluid and low pressure fluid to each of said volume chambers during each relative orbit to define a pressure pattern rotating at the speed of said relative orbital movement between said members, said axial pressure-balancing system comprising:

a. a relatively thin sealing plate in generally sealing engagement with an axial end face of each of said toothed members;

b. a balancing member in engagement with an end face of said sealing plate, said sealing plate being disposed between said toothed members and said balancing members;

0. said sealing plate defining a plurality of fluid passages extending therethrough, each of said fluid passages being in fluid communication with one of said volume chambers;

d. said balancing member defining a plurality of sealed balancing areas, each of said balancing areas being in constant communication with one of said fluid passages and its associated volume chamber to contain, sequentially, both high pressure fluid and low pressure fluid during each relative orbit; and each of said balancing areas being at least slightly larger than said maximum area of said volume chambers, to provide a net force on said sealing plate, in the area adjacent each of said balancing areas, biasing said sealing plate toward sealing engagement with said externally-toothed member to minimize leakage between adjacent volume chambers. 2. The balancing arrangement of claim 1 wherein the outer boundary of each volume chamber is defined as extending about the internal periphery of said internally-toothed member between the centers of adjacent pockets,

each of said ports being positioned midway said outer boundary of each volume chamber and juxtaposed the internal periphery of said ring member, and

the internal periphery of said ring member being sized with respect to said externally-toothed member whereby the apex of the teeth of said externally-toothed member is prevented from closing said ports when and as said members move relative one another.

3. The balancing arrangement of claim 2 wherein each area is defined by inner and outer concentric arcuate seals contiguous with radially-extending side seals to form a generally trapezoidal shaped area, and each port communicates with the center of each area.

4. The balancing arrangement of claim 3 wherein each area is separated from its adjacent area by a radially-extending land, and the center of each particular land is in alignment with the center of each particular roller.

UNiitSl-Elfi STATES PATENT @FHQE CERTEFTQQATE 03F CGRREQTEQN PATENT NO. 1 3,869,228

DATED March 4, 1975 lNVEwTORtS) Nils Einar Saedoerg It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown betow:

Col. 1, line 43: Before "25,291" insert-- m---.

-- C01 line 3= "5/8" should rad-*-"l/8"",

Signed and Scaled this twenty-ninth Day of July 1975 [SEAL] A ttes r.-

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissiuncr uj'larents and Trademarks 

1. An axial pressure-balancing system for use in a rotary hydraulic device of the type including an internally-toothed member and an externally-toothed member eccentrically disposed within said internally-toothed member for relative orbital and rotational movement therebetween, said members defining a plurality of volume chambers by tooth interaction therebetween, each of said volume chambers sequentially expanding and contracting during each relative orbit between said members, each of said volume chambers having a maximum cross-sectional area on a plane generally parallel to the plane of said rotational movement, the device further including commutator-type valve means for sequentially communicating high pressure fluid and low pressure fluid to each of said volume chambers during each relative orbit to define a pressure pattern rotating at the speed of said relative orbital movement between said members, said axial pressure-balancing system comprising: a. a relatively thin sealing plate in generally sealing engagement with an axial end face of each of said toothed members; b. a balancing member in engagement with an end face of said sealing plate, said sealing plate being disposed between said toothed members and said balancing members; c. said sealing plate defining a plurality of fluid passages extending therethrough, each of said fluid passages being in fluid communication with one of said volume chambers; d. said balancing member defining a plurality of sealed balancing areas, each of said balancing areas being in constant communication with one of said fluid passages and its associated volume chamber to contain, sequentially, both high pressure fluid and low pressure fluid during each relative orbit; and e. each of said balancing areas being at least slightly larger than said maximum area of said volume chambers, to provide a net force on said sealing plate, in the area adjacent each of said balancing areas, biasing said sealing plate toward sealing engagement with said externally-toothed member to minimize leakage between adjacent volume chambers.
 2. The balancing arrangement of claim 1 wherein the outer boundary of each volume chamber is defined as extending about the internal periphery of said internally-toothed member between the centers of adjacent pockets, each of said ports being positioned midway said outer boundary of each volume chamber and juxtaposed the internal periphery of said ring member, and the internal periphery of said ring member being sized with respect to said externally-toothed member whereby the apex of the teeth of said externally-toothed member is prevented from closing said ports when and as said members move relative one another.
 3. The balancing arrangement of claim 2 wherein each area is defined by inner and outer concentric arcuate seals contiguous with radially-extending side seals to form a generally trapezoidal shaped area, and each port communicates with the center of each area.
 4. The balancing arrangement of claim 3 wherein each area is separated from its adjacent area by a radially-extending land, and the center of each particular land is in alignment with the center of each particular roller. 